System and method for treatment of soil and groundwater contaminated with pfas

ABSTRACT

A method for the decontamination of water containing one or more PFAS contaminants includes injecting a gas through a diffuser and into the water so as to form a plurality of bubbles in the water, the one or more PFAS contaminants accumulating on the plurality of bubbles. The plurality of bubbles is allowed to rise, forming a foam at the surface of the water. The resulting foam is then collected and transported away from the surface of the water, where it condenses into a liquid and can be treated and/or disposed of.

BACKGROUND OF THE INVENTION

This invention relates to a method and device for the decontamination ofa media, such as groundwater or groundwater and soil, containing per-and polyfluoroalkyl substances (PFAS) and related compounds such as PFASprecursors, collectively referred to as PFAS contaminants. Morespecifically, the invention relates to a system and method forconcentrating and removing PFAS contaminants from soil and groundwater,preferably using in-situ gas injection and collection of the resultingfoam.

PFAS are contained in fire-fighting agents such as aqueous film formingfoams (AFFF) and as such have they been used extensively at facilitiessuch as military bases and airports over the past fifty years. They havealso been used in the manufacture of many consumer goods for greaserepellency and water-proofing. More recently, long-chained PFAS inparticular have been shown to bioaccumulate, persist in the environment,and be toxic to laboratory animals, wildlife, and humans. As a result ofthese observations, on May 19, 2016 EPA established a health advisoryfor the long-chained PFAS constituents; perfluorooctanoate (PFOA) andperfluorooctane sulfonate (PFOS) of 70 parts per trillion in drinkingwater.

PFAS have unique chemistry. The carbon-fluorine bond is one of thestrongest bonds in nature and it is very difficult break. In addition,PFOA and PFOS, for example, have a perfluorinated carbon tail thatpreferentially partitions out of the aqueous (water) phase and an ionicheadgroup that partitions into the aqueous phase. (See FIG. 1.) Thiscauses PFAS to preferentially accumulate at air/water interfaces.

Because of these characteristics, traditional in-situ remediationtechnologies such as chemical reduction, chemical oxidation, andbioremediation have not been shown to be effective in treating PFAS.Thermal treatment can be effective, however very high temperatures areneeded (greater than 1,770 degrees F.) for complete destruction therebymaking in-situ treatment either impracticable or very expensive.Groundwater pump and treat systems can remove PFAS however they are noteffective at removing large amounts of contaminant mass and they arealso very costly since these systems tend to operate over long periodsof time, typically decades. Some success has been reported usingimmobilization where for example PFAS waste is mixed with clay andaluminum hydroxide. Long term success with the technology under in-situconditions has not been demonstrated. Therefore, there is an urgent needfor a method and system capable of treating PFAS contaminated soil andwater in situ.

SUMMARY OF THE INVENTION

The present invention includes a method and system for treating PFAScontaminated media, in particular saturated soil and groundwater. Thisinvention relies on the unique properties of PFAS, namely their tendencyto preferentially accumulate at air/water interfaces as shown in FIG. 1.Generally the method involves injecting a gas such as air into a finebubble diffuser that is placed near the bottom of a groundwater well.Fine (less than 2 mm diameter) bubbles are preferred since they providethe most air to water surface area for the PFAS contaminants toaccumulate from the aqueous phase. Since the bubbles are less dense thanwater, they rise to the water surface where they accumulate as a layerof foam. The foam is removed by applying a vacuum to tube(s) that arelocated in the foam head and above the groundwater table. Once thefoam/air mixture is removed from the well it is piped to a knock-outvessel where the foam condenses to a liquid and the air is discharged.

Given the appropriate site geology and well screen intervals, the methoddescribed above has the additional benefit of providing groundwaterrecirculation since the injected air causes water to migrate up and outof the upper recharge screen (see FIG. 2). Once this happens, water isdrawn into the bottom of the well through an influent screen portion anddischarged through an effluent screen portion at the top of the well,thereby setting up a water recirculation system. The influent andeffluent screen portions can be formed by one or more influent screensthat are separate from one or more effluent screens. However, wells withcontinuous screens can also function in this manner. This increases theradius of influence of the treatment well which means less wells arerequired to treat a given area. Alternatively or in concurrence,groundwater can be pumped using in-well pumps to increase the radius ofinfluence and efficiency of the treatment wells. This technology can beadapted to a variety of site conditions and implemented in source areaswith high PFAS concentrations as well as down-gradient locations withlower PFAS concentrations.

Generally, the system requires a groundwater well screened atappropriate depths based on site-specific geology and PFAS location inthe subsurface. An air injection blower or pump is connected into a finepore diffuser located in the water column. Air is injected into the finepore diffuser where bubbles are created and PEAS partitions into theair/water interfaces of the bubbles. The bubbles rise and form a foam atthe groundwater table. The foam is removed from the well by a vacuumextraction blower or pump. The foam is piped into a sealed knock-outdrum or other knock-out vessel, where it condenses into a liquid and theair is discharged. The liquid concentrate can be further treated usingthermal incineration, for example, either on- or off-site. The airdischarge can be further treated on-site using activated carbon, forexample, if necessary.

This invention can be configured as described above with a network ofvertical wells and with other configurations including but not limitedto a network of horizontal foam generation and collection wells, wellnetworks with separate pumping wells, and groundwater interceptortrenches with vertical or horizontal foam generation and collectionwells. Above-ground configurations are also possible using surfacemounted tanks instead of groundwater wells.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in conjunction with the accompanying figures. It is emphasizedthat, according to common practice, the various features on the drawingsare not to scale. Instead, the dimensions of the various features arearbitrarily expanded or reduced for clarity.

FIG. 1 is a chemical representation of the PFAS contaminates PFOS andPFOA. In addition, this figure shows the preference of PFOS and PFOA toaccumulate at air/water interfaces given their unique chemicalstructure, with a hydrophilic head and hydrophobic tail.

FIG. 2 is a process schematic of an exemplary system for in-situtreatment of PFAS contaminated soil and groundwater using foamgeneration and extraction.

DETAILED DESCRIPTION OF THE INVENTION

Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the details shown. Rather various modifications may be madein the details within the scope and range of equivalents of the claimsand without departing from the invention.

Generally, the present invention includes a method and system forremoving PFAS from contaminated soil and groundwater. The invention isbest understood by referring to FIG. 2. A groundwater well is drilled inan area with PFAS contamination, 1 shows ground surface, 2 indicates thegroundwater level, 3 shows the well bore, and 4 shows the well casing,typically PVC. The well is designed to accommodate site-specificconditions including the contaminate location and site hydrogeology. Inthis particular example, the well is constructed with an upper dischargeor effluent screen 14 and a lower influent screen 15. The rest of thewell is constructed with blank (solid) PVC. Sandpack is also insertedinto the well bore adjacent to the well screens.

A bubble diffuser 6, preferably a fine pore diffuser comprised of aplurality of pores having a nominal pore size of 25 microns or less, isconnected to a positive pressure air blower or pump 5. Air is injectedinto the diffuser 6 which produces bubbles 7. There may be more than onediffuser used especially if the water column in the well is long,generally longer than 10 feet. Alternatively, vertical tube diffuserscan be used. Fine pore diffusers can be made of ceramics, polypropylene,porous materials, or other membrane material.

The air/water interface of the bubbles attract PFAS in the aqueous phaseas the bubbles migrate vertically. Once the bubbles reach thegroundwater surface, they form a layer of foam 8. The foam is removedfrom the well by a foam capturing device 9 which is connected to avacuum source 13, such as a vacuum extraction blower or pump. The foamcapturing device provides additional surface area for foam capture witha larger diameter than the connecting pipe. In its simplestconfiguration, the foam capturing device 9 is an expansion chamberconnected to the end of the vacuum pipe. In addition, a funnel-shapeddevice or fine screen may be inserted below, in, or above the foam headto assist with foam accumulation, concentration, and capture. Morecomplicated configurations may include floating foam capturing devicesthat are made of a floating material connected to a vacuum extractiontube. A device like this would accommodate fluctuating groundwatertables and minimize operation and maintenance. Treatment wells with adeep water table may need to use an in-well pump such as a positive airdisplacement pump to pump foam and/or concentrate to the surface forcollection to overcome vacuum limitations at depth.

The foam is transported by vacuum or positive pressure into a sealedknock-out vessel 10 where it condenses into a liquid 11 and it isperiodically removed through a valve 12 for further treatment by, forexample, high temperature incineration. Air is discharged from thenegative pressure blower or pump 13 where it may be treated usingactivated carbon, for example.

Producing bubbles in the well, as described above, causes the watercolumn in the well to migrate vertically since it is less dense than thesurrounding water. When the well is screened with upper 14 and lower 15screens, groundwater recirculation is produced as shown by groundwaterdischarging from the upper screen in the direction of arrow 17 andrecharging into the lower screen in the direction of arrow 16. Thisincreases the radius of influence of the well and increases the rate ofremoval of PFAS from the subsurface. A well with a continuous screen,wherein a lower part of the screen defines an influent screen portionand an upper part of the screen defines an effluent screen portion, canalso function in this manner. Depending on the site-specifichydrogeology and length of the water column being treated, in-well waterpumps can also be used to recirculate groundwater.

The invention can also be combined with other technologies such asin-situ oxidation to convert PFAS precursors into more extractablesubstances such as PFOA and PFOS, and soil washing to increase PFASdesorption from soil. Gases other than air may also be used includingbut not limited to the addition of nitrogen to enhance foam formationand the addition of an oxidizing gas, preferably ozone, to oxidize PFASprecursors. Thus, in an embodiment of the invention, the gas injectedinto the one or more diffusers is greater than 80% nitrogen by volume,preferably 95% or more nitrogen, and more preferably 99% or morenitrogen. Amendments such as surfactants may also be injected into thetreatment area to increase the removal of PFAS, especially short-chainPFAS.

The following examples, which constitute the best mode presentlycontemplated by the inventor for practicing the present invention, arepresented solely for the purpose of further illustrating and disclosingthe present invention, and are not to be construed as a limitation onthe invention.

Groundwater samples from two sites (designated as N000 and Z000) withPFAS contamination were used for laboratory test to demonstrate theperformance of the invention. The analytical data for these sites isshown below.

TABLE 1 Site N000 PFAS Concentrations Analyte Carbon # Units Initial 6:2Fluorotelomer sulfonate 6 ug/L 0.0069 8:2 Fluorotelomer sulfonate 8 ug/LBDL Perfluorobutane Sulfonate (PFBS) 4 ug/L 0.27 Perfluorobutanoic acid4 ug/L 0.14 Perfluorodecane Sulfonate 6 ug/L 0.0072 PerfluorodecanoicAcid (PFDA) 10 ug/L 0.0057 Perfluorododecanoic Acid (PFDoA) 11 ug/L BDLPerfluoroheptanoic Acid (PFHpA) 7 ug/L 0.22 Perfluorohexane Sulfonate(PFHxS) 6 ug/L 5.7 Perfluorohexanoic Acid (PFHxA) 6 ug/L 0.93Perfluoro-n-Octanoic Acid (PFOA) 8 ug/L 1.7 Perfluorononanoic Acid(PFNA) 9 ug/L 0.055 Perfluorooctane Sulfonamide (PFOSA) 8 ug/L BDLPerfluorooctane Sulfonate (PFOS) 8 ug/L 1.6 Perfluoropentanoic Acid(PFPeA) 5 ug/L 0.31 Perfluorotetradecanoic Acid 14 ug/L BDLPerfluorotridecanoic Acid 13 ug/L BDL Perfluoroundecanoic Acid (PFUnA)11 ug/L BDL Note: BDL = Below Detection Limit

TABLE 2 Site Z000 PFAS Concentrations Analyte Carbon # Units Initial 6:2Fluorotelomer sulfonate 6 ug/L 2.8 8:2 Fluorotelomer sulfonate 8 ug/LBDL Perfluorobutane Sulfonate (PFBS) 4 ug/L 200 Perfluorobutanoic acid 4ug/L 44 Perfluorodecane Sulfonate 6 ug/L BDL Perfluorodecanoic Acid(PFDA) 10 ug/L BDL Perfluorododecanoic Acid (PFDoA) 11 ug/L BDLPerfluoroheptanoic Acid (PFHpA) 7 ug/L 36 Perfluorohexane Sulfonate(PFHxS) 6 ug/L 1300 Perfluorohexanoic Acid (PFHxA) 6 ug/L 270Perfluoro-n-Octanoic Acid (PFOA) 8 ug/L 66 Perfluorononanoic Acid (PFNA)9 ug/L BDL Perfluorooctane Sulfonamide (PFOSA) 8 ug/L BDLPerfluorooctane Sulfonate (PFOS) 8 ug/L 490 Perfluoropentanoic Acid(PFPeA) 5 ug/L 51 Perfluorotetradecanoic Acid 14 ug/L 7Perfluorotridecanoic Acid 13 ug/L 4.9 Perfluoroundecanoic Acid (PFUnA)11 ug/L BDL Note: BDL = Below Detection Limit

As can be seen from the above tables, the sites have similar types ofPFAS, the primary difference is the concentrations, where site Z000 hasmuch higher concentrations that are indicative of a source area nearby.

Laboratory batch tests were conducted in one-liter graduated cylindersas a model for the groundwater treatment wells shown in FIG. 2. The testvessels were sparged with air or nitrogen (99% by volume) which produceda layer of foam on top of the water column that was subsequently removedby a collection tube placed under vacuum. The gases were sparged intothe groundwater using either a Small or Large Diffuser. A ceramic finebubble diffuser with nominal pore size of 25 microns was used as theLarge Diffuser and a stainless steel porous metal sparger tube with anominal pore size of 5 micron was used as the Small Diffuser. Bothdiffusers had similar surface areas. Diffusers with larger pore sizeswere tested; however, it was determined that they were not able toproduce acceptable foams. The remaining water in the test vessel wasthen sent for PFAS analysis using EPA Method 537 (modified).

TEST 1: The first experimental test was designed to demonstrate theeffectiveness of air in removing PFAS from water. The Large Diffuserwith a nominal pore size of 25 microns was used in this test. Theexperimental test conditions and results for this testing are shown inTable 3. PFHxS, PFOA, and PFOS were used as PFAS indicators for thesetests.

TABLE 3 Effectiveness of Air Sparging, Large Diffuser, Z000 GroundwaterFlow Rate, Run Time, PFHxS, PFOA, PFOS, L/min min ug/l ug/l ug/l Initial4 4 1,300 66 490 Concentration Final 71 2.0 20 Concentration % Reduction−95% −97% −96%

As can be seen in Table 3, air was very effective in removing PFAS fromwater under these test conditions.

TEST 2: The second experimental test was set-up to investigate thedifference between air and nitrogen sparging. It was hypothesized thatunder the same conditions, nitrogen should be more efficient than airsince nitrogen is non-reactive and tends to form smaller bubbles thanair when injected in water. The Large Diffuser with a nominal pore sizeof 25 microns was used in this test. The experimental test conditionsand results for this testing are shown in Table 4. PFHxS, PFOA, and PFOSwere used as PFAS indicators for these tests.

TABLE 4 Air vs. Nitrogen Performance Comparison, Large Diffuser, Z000Groundwater Flow Run PFHxS, ug/l, PFOA, ug/l, PFOS, ug/l, Rate, Time,Concentrate, Final Final Final L/min min ml Concentration ConcentrationConcentration Air 4 4 140 83 2.3 31 Nitrogen 2 4 150 71 2.0 20 % −14%−13% −35% Difference

As can be seen in Table 4, nitrogen outperformed air with similar runtimes of 4 minutes and PFAS foam volumes ranging from 140 to 150 ml.However nitrogen was able to produce a similar volume of concentrate atone-half the flow rate of air and water PFAS concentrations that wereless than the air sparged system. This test showed that nitrogen wasmore efficient than air in removing PFAS from water under these testconditions.

TEST 3: The third experimental test evaluated the difference of gasbubble size in PFAS removal from water. It was hypothesized that underthe same conditions, small bubbles would be more efficient in removingPFAS from water than larger bubbles, since smaller bubbles have moretotal surface area and enhance the likelihood of contact of PFAS with agas bubble in the water column.

The experimental conditions are summarized in Table 5. PFHxS, PFOA, andPFOS were used as PFAS indicators for these tests. A ceramic fine bubblediffuser with nominal pore size of 25 microns was used as the LargeDiffuser and a stainless steel porous metal sparger tube with a nominalpore size of 5 micron was used as the Small Diffuser. As a point ofreference, the Large Diffuser produced bubbles averaging about 1 mm indiameter whereas the Small Diffuser produced bubbles averaging about 0.2mm in diameter.

TABLE 5 Large Diffuser vs. Small Diffuser, Nitrogen, Z000 GroundwaterPFHxS, PFOA, PFOS, Flow Run ug/l, Final ug/l, Final ug/l, Final Rate,Time, Concen- Concen- Concen- L/min min tration tration tration Large 24 71 2.0 20 Diffuser Small 2 4 9.4 0.46 3.8 Diffuser % Difference −87%−77% −81%

As can be seen in Table 5, the Small Diffuser outperformed the LargeDiffuser in PEAS removal from water by a considerable margin. Theconclusion from this test was that the Small Diffuser with <1 mmdiameter bubbles was much more efficient that the Large Diffuser with >1mm diameter bubbles in removing PFAS from water under these testconditions, even though both are considered fine bubble diffusers.

TEST 4: The fourth experimental test was set-up to evaluate usingnitrogen and the Small Diffuser to remove low levels of PFAS using thelow concentration (N000) groundwater. As with previous nitrogen tests,the flow rate was set at 2 liters per minute and the test was run for 4minutes. To further evaluate the data, removal efficiencies for allmeasured PFAS are shown below in Table 4 below. They are arrangedaccording to carbon chain length.

TABLE 6 Low Concentration (N000 Groundwater) PFAS Removal by CarbonNumber, Small Diffuser, Nitrogen Carbon % Reduc- # Units Initial Finaltion Perfluorobutane 4 ug/L 0.27 0.27 No Sulfonate (PFBS) Reduc- tionPerfluorobutanoic 4 ug/L 0.14 0.13  7% acid Perfluoro 5 ug/L 0.31 0.33No pentanoic Reduc- Acid (PFPeA) tion 6:2 Fluorotelomer 6 ug/L 0.0069 J0.0032 U 54% sulfonate Perfluorohexane 6 ug/L 5.7 2.7 53% Sulfonate(PFHxS) Perfluorohexanoic 5 ug/L 0.93 0.89  4% Acid (PFHxA)Perfluoroheptanoic 7 ug/L 0.22 0.16 27% Acid (PFHpA) Perfluoro-n- 8 ug/L1.7 0.65 62% Octanoic Acid (PFOA) Perfluorooctane 8 ug/L 1.6 0.26 84%Sulfonate (PFOS) Perfluorononanoic 9 ug/L 0.055 0.0046 U 92% Acid (PFNA)Note: U = Below Detection Limit so percent reductions may have beengreater than the reported value.

As can be seen in Table 6, PFAS was removed from water under theseexperimental conditions, even though the starting concentrations weresubstantially less than the previous tests using Z000 groundwater.Another observation is that the PFAS removal efficiency appears toincrease as the PFAS carbon chain length increases. It appears that,since the mechanism of separation occurs at the air/water interface, thelong chain PFAS are removed more efficiently than the short chain PFAS.This led to the design of TEST 5 described below, to further investigatethis observation.

TEST 5: A fifth test was set-up to determine if experimental conditionscan be optimized for both short and long chain PFAS removal. Z000groundwater was used for this evaluation. As with previous nitrogentests, the flow rate was set at 2 liters per minute and the test was runfor 4 minutes.

As a basis of comparison, the results from TEST 1 are presented in anexpanded PFAS format showing all measured PFAS and arranged according tocarbon chain length as shown in Table 7.

TABLE 7 High Concentration (Z000 Groundwater) PFAS Removal by CarbonNumber, Large Diffuser, Air % Reduc- Analyte Carbon # Units InitialFinal tion Perfluorobutane 4 ug/L 200 160 20% Sulfonate (PFBS)Perfluorobutanoic 4 ug/L 44 39 11% acid Perfluoropentanoic 5 ug/L 51 4414% Acid (PFPeA) 6:2 Fluorotelomer 6 ug/L 2.8 0.20 U 93% sulfonatePerfluorohexane 6 ug/L 1300 71 95% Sulfonate (PFHxS) Perfluorohexanoic 6ug/L 270 170 37% Acid (PFHxA) Perfluoroheptanoic 7 ug/L 36 5.8 84% Acid(PFHpA) Perfluoro-n- 8 ug/L 66 2.0 97% Octanoic Acid (PFOA)Perfluorooctane 8 ug/L 490 20 96% Sulfonate (PFOS) Perfluorotridecanoic13 ug/L 4.9 0.28 U 94% Acid Perfluorotetradecanoic 14 ug/L 7 0.22 U 97%Acid Note: U = Below Detection Limit so percent reductions may have beengreater than the reported value.

This experimental test was set-up to evaluate using nitrogen and theSmall Diffuser to remove PFAS using the high concentration (Z000)groundwater. As with previous nitrogen tests, the flow rate was set at 2liters per minute and the test was run for 4 minutes.

TABLE 8 High Concentration (Z000 Groundwater) PFAS Removal by CarbonNumber, Small Diffuser, Nitrogen % Reduc- Analyte Carbon # Units InitialFinal tion Perfluorobutane 4 ug/L 200 53 74% Sulfonate (PFBS)Perfluorobutanoic 4 ug/L 44 15 66% acid Perfluoropentanoic 5 ug/L 51 1865% Acid (PFPeA) 6:2 Fluorotelomer 6 ug/L 2.8 0.032 U 99% sulfonatePerfluorohexane 6 ug/L 1300 9.4 99% Sulfonate (PFHxS) Perfluorohexanoic6 ug/L 270 43 88% Acid (PFHxA) Perfluoroheptanoic 7 ug/L 36 0.79 98%Acid (PFHpA) Perfluoro-n- 8 ug/L 66 0.46 99% Octanoic Acid (PFOA)Perfluorooctane 8 ug/L 490 3.8 99% Sulfonate (PFOS) Perfluorotridecanoic13 ug/L 4.9 0.033 U 99% Acid Perfluorotetradecanoic 14 ug/L 7 0.038 U99% Acid Note: U = Below Detection Limit so percent reductions may havebeen greater than the reported value.

As illustrated by the data in Table 8, these test conditions greatlyincreased the PFAS removal efficiency for all PFAS as compared to thePFAS removal efficiencies shown in Table 7. There is some apparentpreference for long chain PFAS removal over short chain PFAS removal,however this data shows that it is possible to remove long and shortcarbon chain PFAS by optimizing the performance of the Invention.

Optimization techniques may include adjusting injected gas bubble sizeand gas composition as shown in the preceding tests. In addition,contact time can be increased. This is particularly relevant for fieldapplication since most treatment wells will have longer bubble columnsthan the test vessels used in these experiments. For example, thelaboratory test vessels had a column (bubble) height of one foot whereasa treatment well installed in the field will have a column (bubble)height of at least ten feet. In addition, based in typical groundwaterflow rates, the contact time for treatment wells installed in the fieldwill typically range from hours to days as opposed to the minutetimeframes used in the laboratory experiments. Therefore even though thelaboratory tests results showed good PFAS removal performance, evenhigher PFAS removal performance is expected in the field.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings) may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

What is claimed:
 1. A method for the decontamination of water containingone or more PFAS contaminants, comprising: injecting a gas through adiffuser and into the water so as to form a plurality of bubbles in thewater, the one or more PFAS contaminants accumulating on the pluralityof bubbles; allowing the plurality of bubbles to rise, forming a foam atthe surface of the water; and collecting the foam from the surface ofthe water.
 2. The method of claim 1, wherein the diffuser is positionedwithin a groundwater well and below the surface of the groundwater whenthe gas is injected through the diffuser and into the water.
 3. Themethod of claim 2, wherein the groundwater well is provided with atleast one influent screen portion and at least one effluent screenportion.
 4. The method, of claim 1, further comprising, prior toinjecting the gas through the diffuser, creating a groundwater well andpositioning the diffuser within the groundwater well and below thesurface of the groundwater.
 5. The method of claim 1, wherein the gas isinjected through a diffuser and into the water so as to form a pluralityof bubbles in the water that are less than 2 mm in diameter.
 6. Themethod of claim 1, wherein the diffuser is comprised of a plurality ofpores having a nominal pore size of 25 microns or less.
 7. The method ofclaim 1, further comprising transporting the foam to a knock-out vesselwhere condensed liquid containing the one or more PFAS contaminants iscollected.
 8. The method of claim 7, further comprising removing thecondensed liquid containing the one or more PFAS contaminants from theknock-out vessel and treating the one or more PFAS contaminants.
 9. Themethod of claim 7, wherein the knock-out vessel is in communication witha vacuum source.
 10. The method of claim 1, wherein the gas is comprisedof air.
 11. The method of claim 1, wherein the gas is more than 80%nitrogen.
 12. The method of claim 1, wherein the gas is 95% or morenitrogen.
 13. The method of claim 1, wherein the gas is 99% or morenitrogen.
 14. The method of claim 1, wherein the foam is collected fromthe surface of the water by a foam capturing device that is incommunication with a vacuum source.
 15. The method of claim 2, furthercomprising transporting the foam to a knock-out vessel by a positivedisplacement pump positioned in the groundwater well.
 16. The method ofclaim 1, wherein an oxidizing gas is added to the gas before it isinjected into the diffuser, the oxidizing gas being utilized to oxidizePFAS precursors.
 17. The method of claim 16, wherein the oxidizing gasis ozone.
 18. The method of claim 1, wherein the foam is collected fromthe surface of the water with a foam capturing device that providesadditional surface area for foam capture with a larger diameter than apipe connected to the foam capturing device.
 19. The method of claim 18,wherein the foam capturing device is comprised of a floating material soas to accommodate fluctuating groundwater tables.
 20. The method ofclaim 1, wherein the one or more PFAS contaminants are one or morelong-chain PFAS constituents.
 21. The method of claim 1, wherein the oneor more PFAS contaminants are one or more short-chain PFAS constituents.22. The method of claim 1, wherein the one or more PFAS contaminants arecomprised of PFOA or PFOS or both.